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## Homework Statement

I'm having trouble solving the following exercise:

Given the following wave equation:

y=0.01cos(wt-kx)+0.02*6^(1/2)sin(wt-kx)

prove that if w=16s^-1 and k=6m^-1 then the amplitude of the wave is 0.05 meters and the initial phase is -pi/4 how can I prove that? By phasor addiction probably but I can't go far that way. can someone show me how to do it?

Thank you

## Homework Equations

## The Attempt at a Solution

I converted sin(wt-kx) to cos(wt-kx-pi/2) so I can write the phasor corresponding to each cosine and attempt to add then an see what I get back, but what I get back I the equation I started with with the cos(wt-kx-pi/2) back as sin(wt-kx) by looking att the trignometric identity: acos(A)+bsin(B)=[tex]\sqrt{b^2+a^2}[/tex]*sin(A+C) where C is arctan([tex]\frac{b}{a}[/tex]) i could get the amplitude, but the phase I get is diffrent.